Antigen Recognition by Variable Lymphocyte Receptors (VLR) in the Sea Lamprey

重组适应性免疫系统出现在5亿年前脊椎动物辐射的曙光时期。颌骨脊椎动物通过免疫球蛋白(Ig)基因片段的V(D)J重排产生不同的B和T细胞抗原受体。与之形成鲜明对比的是，无颌脊椎动物，如七鳃鳗，通过重组插入不同的富含亮氨酸重复序列(LRR)的模块单元来组装它们的可变淋巴细胞受体(VLR)，从侧翼盒到胚系VLR基因。该谱系的组合多样性约为1014个独特的抗原受体，包括LRR和基于Ig的适应性免疫系统。考虑到没有颌骨和有颌骨的脊椎动物是寒武纪仅存的两个脊椎动物分类群，这一点很耐人寻味。进化出不是一种而是两种不同类型的重排淋巴细胞抗原受体的选择压力是多少？VLR和抗体进化是否是偶然和必要的，以识别抗原世界的相似或不同决定因素？本课题将探讨VLRs在七鳃鳗免疫中的作用。VLR的抗原识别将在用各种类型的抗原免疫刺激的动物中进行研究，这些抗原包括外来蛋白、微生物细胞壁成分以及微生物DNA和RNA。我们将从免疫动物的淋巴细胞中构建VLRs文库，以筛选那些能与抗原高度特异性结合的受体。选定的VLR与其同源配体结合后将被结晶，以确定络合物的三维结构，并鉴定VLR与其配体之间的接触残基。VLR的功能和结构特征可能有助于阐明获得性免疫的起源，特别是因为LRR模块也是我们自己的主要天然微生物检测受体的构建块，如Toll样受体和细胞质中的NBS-LRR家族成员，以及含有LRR的植物抗病基因。该项目将对不同学术背景的几名学生进行培训。此外，潘瑟博士还将把他的研究成果用于教授比较和进化免疫生物学课程。

Two types of recombinatorial adaptive immune systems appeared at the dawn of vertebrate radiation ~500 million years ago. Jawed vertebrates generate a diverse repertoire of B and T cell antigen receptors through V(D)J rearrangement of immunoglobulin (Ig) gene fragments. In sharp contrast, jawless vertebrates such as the sea lamprey, assemble their variable lymphocyte receptors (VLR) through recombinatorial insertion of diverse leucine-rich repeat (LRR) modular units, from flanking cassettes into the germline VLR gene. The combinatorial diversity of the repertoire is about 1014 unique antigen receptors, both for the LRR and the Ig-based adaptive immune systems. This is intriguing when considering that jawless and jawed vertebrates are the only two vertebrate taxons that survived from the Cambrian period. What was the selective pressure to evolve not one but two different types of rearranging lymphocyte antigen receptors? Did VLRs and antibodies evolve by chance and necessity to recognize similar, or perhaps different determinants of the antigenic world? The role of VLRs in lamprey immunity will be explored in this project. Antigen recognition by VLR will be studied in animals immunostimulated with various types of antigens, including foreign proteins, microbial cell wall components, and microbial DNA and RNA. Libraries of VLRs will be constructed from lymphocytes of immunized animals, to select those receptors that can bind the antigens with high specificity. Selected VLRs bound to their cognate ligand will then be crystallized, to determine the three-dimensional structure of the complexes, and to identify contact residues between the VLR and its ligand. Functional and structural characterization of the VLR may help elucidate the origin of adaptive immunity, in particular since LRR modules are also the building blocks of our own cardinal innate microbial detection receptors, such as the Toll-like receptors and the cytoplasmic NBS-LRR family members, and the LRR-containing Disease Resistance genes of plants. This project will involve the training of several students at varying academic backgrounds. In addition, Dr. Pancer will incorporate his research results in teaching a course in comparative and evolutionary immunobiology.